Riboflavin improves postharvest cold tolerance in zucchini fruit inducing non-enzymatic antioxidant response and phenolic metabolism

This work was supported by research grant PID2020-118080RB-C22 of the Ministry of Science and Innovation (Spanish Government). Alejandro Castro-Cegrí was supported by Contrato-Puente from the Plan Propio of the University of Granada and Alicia García received a Margarita Salas postdoctoral fellowship (RR_A_2022_05) of ‘Ministerio de Universidades’ funded by NextGenerationEU program. Funding for open access charge: Universidad de Granada/CBUA.

The storage of zucchini fruit at low temperatures during postharvest induces a physiological disorder called chilling injury that drastically reduces fruit quality and shelf life. The phytohormone abscisic acid (ABA) is involved in the acquisition of cold tolerance in zucchini fruit, being the riboflavin pathway one of the most differentially induced with ABA treatment. Thus, the aim of this work was to elucidate the involvement of riboflavin in quality maintenance of zucchini fruit during postharvest cold storage. After testing different concentrations of exogenous riboflavin, 0.5 mM showed the best results. Riboflavin treatment reduced H2O2 content, but the enzymatic antioxidant defense did not change significantly. This response is due to a rise of nonenzymatic antioxidant defense, by accumulating metabolites like ascorbate and carotenoids, as well as inducing phenolic metabolism. The application of this vitamin enhanced the phenolic and flavonoid content in fruit, concomitant with an induction of PAL and C4H activities and an inhibition of PPO activity. This enhancement of the phenylpropanoid pathway resulted in high vanillic acid and quercetin levels at first day of cold storage. The induction of numerous antioxidant compounds and abscisic acid by riboflavin treatment at short-term postharvest period could be responsible for the lack of chilling injuries in zucchini fruit. Therefore, riboflavin could be successfully implemented in the food industry as an alternative to physical or chemical treatments, due to it is an innocuous additive with good water solubility and low cost, as it prolongs the shelf-life of zucchini fruit and increases its nutraceutical properties.

Ministry of Science and Innovation PID2020-118080RB-C22

Plan Propio of the University of Granada

NextGenerationEU program (RR_A_2022_05)

Universidad de Granada/CBUA